The present claimed invention relates to the field of position determination systems. More specifically, the present claimed invention relates to an improved position determination device and radio relay device.
A typical differential global positioning system (DGPS) network includes a receiver which receives ephemerides data from satellites. Typically, such data is received from global positioning system (GPS) satellites which are a part of the GPS satellite network or satellites which are a part of the Global Navigation Satellite System(GLONASS). The ephemerides data is processed via an electronics package located within the GPS unit. The GPS unit receives differential correction data through a separate radio which is typically connected to the GPS unit by cable. The differential correction data is typically obtained from a radio coupled to a GPS unit which is located at a fixed site which is placed at a known location or it is obtained from other sources and is conveyed via radio. By processing the differential correction data together with the data received at the particular GPS receiver, the location of the GPS unit may be determined within a high degree of accuracy. This same method may be used to perform real time kinematic (RTK) surveys so as to accurately determine the relative position of the GPS system with sub centimeter accuracy.
Prior art GPS devices used in DGPS applications and RTK applications typically require numerous separate, distinct component units which are connected via cables. For example, the GPS receiver and processor would constitute one unit and the terrestrial radio would constitute a second unit which would be coupled to the GPS processor via cable. Typically, an input/output (I/O) unit which includes a display for data monitoring and a keypad for data input is also required. The I/O unit is coupled to the GPS receiver/processor unit and to the terrestrial radio via cable. Some systems also require the attachment of a separate battery via cable. Because multiple separate units are used in these prior art systems, the systems are bulky and they are difficult to move around.
For example, one type of prior art system which is typically referred to as xe2x80x9chandheldxe2x80x9d includes a GPS antenna, a GPS processor, a display processor, and a display in a single unit. A DGPS radio antenna and receiver are provided in a separate unit or units which are connected to the GPS processor. Another type of prior art system places the GPS antenna in an antenna unit and the display in a separate display unit. The GPS processor and the display processor may be contained in the GPS antenna unit, the display unit, or in a separate unit. A DGPS radio antenna and receiver are provided in a separate unit or units connected to the GPS processor. This format allows the user to separate the GPS antenna and the display units so that the GPS position and time information can be observed and operated upon in a protected environment.
The use of multiple units to house the various components required for prior art DGPS systems, and the requirement for cables and connectors to couple the units creates problems regarding reliability and durability. This is particularly true for DGPS systems which are mobile and which are jarred and shaken by use and movement. In addition, the systems are expensive to manufacture and assemble. Furthermore, the connections are often bulky, expensive and prone to breakage or malfunction. In addition, it is difficult to move the various boxes and cables around.
Typically, the GPS unit receivers are separated by long distances or by immobile structures; therefore, radio relay units are used to get the signal from one GPS unit to anther GPS unit. Prior art radio relay systems for relaying GPS signals typically include multiple separate components such as a transceiver operating at one frequency which is coupled via cable to a separate transceiver operating at a second frequency. These relay systems typically receive signals through an antenna which is cabled to a processor which is then cabled to a radio which rebroadcasts the signal through an antenna attached by cable to the radio. These relay systems are bulky and difficult to move around. Furthermore, these relay systems typically are expensive and are difficult to maintain and operate due to the fact that each of the components of the radio relay system is unique. In addition, most of the currently available systems are not durable and reliable enough for applications such as RTK surveying and operation in harsh environments such as construction sites.
Some recent prior art systems include GPS components that are attached to a range pole. However, in these recent prior art systems, much of the weight is located at or near the top of the range pole. This makes the system difficult to carry around and operate because the system tends to tip over. This can damage the system if it results in the operator dropping the system. At a minimum, this results in operator muscle fatigue because the operator has to constantly fight the system""s tendency to tip over.
What is needed is a simple GPS network which is easy to move from place to place and which is durable, reliable, and inexpensive to manufacture and assemble. More specifically, a GPS network which includes a GPS unit, a radio and a radio relay which will reliably operate in difficult environments such as those presented by repeated movement and use in harsh environments such as construction sites is required. Also, a GPS network consisting of components which are easy to operate, use and maintain is required. Moreover, a system is needed that is mounted on a range pole and that does not easily tip over or produce operator muscle fatigue.
The present invention meets the above need with a position determination system which includes a position determination device which can be easily moved and which can be easily and cheaply manufactured and assembled. The above achievement has been accomplished by using a single integrated structure to house the position determination antenna the GPS receiver, a power conditioning system, the position determination processor, and the DGPS radio antenna and DGPS radio circuit board. The position determination device may be easily converted to a radio relay by altering the components located within the housing. The resulting position determination network includes an integrated position determination device and radio relay combination which will reliably operate in difficult environments and which is easy to operate, use and maintain.
A position determination network which includes all of the elements required for DGPS position determination and RTK is disclosed. The network includes a position determination device which holds all of the components necessary for position determination and RTK using DGPS techniques within a single housing. Though the position determination system may be operated using any of a number of different sources of telemetry signals such as GLONASS and the like, the positioning system will be herein described with reference to the use of GPS satellites for purposes of clarity. The GPS satellites include information on the ephemerides of each GPS satellite, parameters identifying the particular GPS satellite, and corrections for ionospheric signal propagation delays. A useful discussion of the GPS and techniques for obtaining position information from the satellite signals is found in Tom Logsdon, The Navstar Global Positioning System, Van Nostrand Reinhold, 1992, pp. 17-90, incorporated by reference herein. Reference to a Global Positioning System or GPS herein refers to a Global Positioning System, to a GLONASS system, and to any other compatible satellite based system that provides information by which an observers position and/or the time of observation can be determined. Further information regarding GPS position determination is contained in U.S. Pat. No. 5,519,620 by Nicholas Talbot et al. entitled CENTIMETER ACCURATE GLOBAL POSITION SYSTEM RECEIVER FOR ON-THE-FLY REAL TIME KINEMATIC MEASUREMENT AND CONTROL which is incorporated herein by reference.
The term xe2x80x9cDGPSxe2x80x9d as used herein and xe2x80x9cDGPS radiowavexe2x80x9d signal as used herein includes electromagnetic signals containing GPS differential correction information transmitted by other GPS units and/or systems, by the Coast Guard DGPS network, by radio beacon signals, by FM subcarrier signals, by digital subcarrier on an analog two-way radio, by digital radio signals, by cellular telephone signals, by digital cellular telephone signals, by private and semi private network signals that use terrestrial and/or satellite apparatus for transmitting DGPS signals for correction of the GPS location and/or time information.
A first embodiment includes a GPS antenna, GPS/DGPS processing circuitry, a radio and a radio antenna. A power supply battery is placed into a cylindrical pole which is attached to the bottom of the housing so as to form a complete, portable, self-contained GPS system. A display panel includes an on/off switch and lighted indicators. A separate display unit is coupled to the GPS unit for display of position information. Communication between the display unit and the GPS unit may be by cable, communication link, or infrared methods. The separate display unit contains its own power source. However, in one embodiment, the display unit is powered by the GPS unit through the GPS unit""s power supply.
A second embodiment is disclosed in which a tripod base instead of a pole is mounted to the housing. The tripod base includes a location mechanism which is used to precisely locate the GPS system with respect to a monument. The location mechanism may be a prismatic optical finder, a laser optical finder, a fixed height tripod, or a laser finder implemented in a tripod with a fourth leg. The tripod base includes a battery pack mounted on or within the tripod. This second embodiment may be used to precisely align a GPS system over a given reference point such as an United States Geological Survey (USGS) site. This allows for easy precise location of a GPS system. The housing and all of the components within the housing are the same as those disclosed in the first embodiment. Thus, the parts are interchangeable. This allows for economies of scale in manufacturing, easy assembly and maintenance, and allows for flexible use of the position determination network components in multiple applications.
In a third embodiment a radio relay unit is disclosed which uses many of the same components as do the first two embodiments. The radio relay unit includes a radio antenna, radio processing circuitry, and a power supply. A transceiver may be installed into the radio relay unit for transmitting and receiving DGPS correction information at the same frequency, or at a different frequency. DGPS correction information may be transmitted either from a second GPS unit or from other sources. This correction data may then be received directly by a GPS unit. Alternatively, the correction data may be received by a radio relay unit which then rebroadcasts the correction information. A GPS unit then receives the rebroadcast correction information on the radio contained within the GPS unit. Alternatively, multiple relay units may be used to transmit correction information over larger distances. Since the radio relay unit uses many of the same components used in the GPS unit, components between the first two embodiments and the third embodiment may be used interchangeably. In addition, the batteries, poles and tripods may be used interchangeably depending on the requirements of a particular project.
A position determination network which includes both the first, the second, and the third embodiments of the present invention is also disclosed. In this network a first GPS system consisting of a GPS unit mounted on a tripod is used as a base station and is located over a known location using the finder located in the tripod. A radio relay system composed of a radio relay unit mounted on a tripod is located within radio range from the first GPS system. A second radio relay system is placed near the site where locations are to be determined. Additional radio relays may be used to extend the range even further. A GPS system including a GPS unit mounted on a pole is then used to pinpoint the desired geographic location or locations.
Since the GPS antenna, GPS radio circuitry, GPS and DGPS processing circuitry, power conditioning system, radio, and radio antenna are integrated into a single housing, a GPS system which is easy to move, easy to use, and easy to assemble and disassemble is obtained. In addition, a more durable and reliable GPS unit results due to the shielding and protection of the various components resulting from the integration of the various components into a single housing. Since many of the components are common to both the GPS system and the radio relay system, the position determination network allows for inexpensive manufacturing of the required components. The GPS system and the radio relay system are easy to assemble and easy to repair due to the usage of a common assembly scheme and due to the use of common components. In addition, due to the design of the system and since a single housing is used, the GPS system and the radio relay system are more reliable and durable than the multiple cable connected units found in prior art systems.
In one embodiment, an integrated position determination system and communication system is described that includes a range pole and in which the various components are coupled to the range pole such that the system is both horizontally and vertically balanced. Because the system is both horizontally and vertically balanced, when a user grips the range pole, there is no tendency for the system to tip over. This prevents potential damage to the system from the system falling over and minimizes or eliminates muscle fatigue as typically occur with prior art systems.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.